This application is a division of our copending application Ser. No. 665,924 filed Mar. 11, 1976, now U.S. Pat. No. 4,028,707, which is a continuation-in-part of our application Ser. No. 437,927 filed Jan. 30, 1974, now U.S. Pat. No. 3,967,282.
In U.S. Pat. No. 3,967,282, an Underground Pipe Detection System is described which utilizes an antenna described in detail in copending U.S. application Ser. No. 665,924 filed Mar. 11, 1976. The operation of this detector system depends at least in part on the generation of a high voltage pulse of significantly short duration, for example, in the range of 150 pico-seconds. Resonse of the antenna system to a pulse transmitted therethrough under these conditions becomes difficult to ascertain. Consequently, the noted patent teaches an arrangement wherein the reflections from successively generated transmit pulses are sampled or analyzed at progressively increasing intervals. These intervals, however, have a consistent repetition over the broader interval designated by the sweep-period of a readout circuit.
To achieve the requisite timing for sampling intervals, a series of fast ramp signals are compared with a simultaneously generated relatively slow ramp controlling circuit of the readout system to define progressively varying points of voltage equivalents between the ramps. With such an arrangement, a periodic sampling of reflected waves is carried out. In consequence of this, transmitted and received detecting signals, even though formed within an extremely narrow time interval, may be analyzed with effectiveness to derive an output representative of the location of objects buried beneath the terrestrial surface.
Obviously, it is necessary to synchronize transmission of the very narrow and extremely high voltage transmission pulse with the readout system associated with the antenna and transmitting media. For this purpose, the coaxial cable leading from the pulse generator must be operated upon in some manner wherein a properly synchronized input triggering the noted fast ramp generator is derived.
Conventional approaches to achieving an appropriate synchronization, for example, by monitoring a triggering network, are not available, inasmuch as the noted high voltage transmission pulses are generated somewhat randomly.